Step 1: Preheat your oven to 350°F (175°C) to ensure even baking.
Step 2: Line your 9x9 inch baking pan with parchment paper, leaving some overhang for easy removal.
Step 3: Melt the butter in a microwave-safe bowl. In another bowl, melt the butterscotch chips at 70% power, stirring every 30 seconds until smooth.
Step 4: Combine the melted butter, dark brown sugar, and melted butterscotch chips in a large mixing bowl. Whisk until smooth, then add the egg and vanilla extract, mixing well.
Step 5: In a separate bowl, whisk together the flour, baking soda, and salt. Gradually add to the wet ingredients, stirring just until combined.
Step 6: Gently fold in the white chocolate chips using a rubber spatula.
Step 7: Pour the batter into the prepared baking pan and spread evenly. Bake for 20-25 minutes, or until the edges are golden and a toothpick comes out with a few moist crumbs.
Step 8: Allow to cool in the pan for about 10 minutes, then lift out using the parchment and cool completely on a wire rack before cutting into squares.
